The use of PdCu-based dental ceramic alloys has been linked to frequent incidence of allergy and hypersensitivity reactions. Whereas Pd has been suspected as the causative factor, the biological safety of other Pd- containing alloys has not been a matter of concern. The broad objective of this study is toe understand the reason why the PdCu-based alloy pose significantly greater risks to patients than some other alloys that also contain Pd. Corrosion is thought to play a major role in allergy and other alloys that also contain Pd. Corrosion is thought to play a major role in allergy and hypersensitivity. Therefore, a systematic study of the corrosion mechanism of selected Pd-containing alloys is proposed. The specific aims are (1) to study in vitro the corrosion behavior of 15 commercial and 9 experimental pd-containing alloys and their components in a synthetic saliva solution at 37 degrees Centrigrade, (2) to characterize the structural and compositional changes on the surface of these alloys due to corrosion, and (3) to determine the concentration of various metal ions released from these alloys during corrosion. The corrosion behavior will be studied by a number of electrochemical techniques and immersion tests. The electrochemical techniques will include (1) open-circuit-potential time measurement, (2) polarization corrosion test. Alloys subject to immersion and potentiostatic corrosion test will be examined and analyzed selectively by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS), to define the corrosion- induced structural and compositional changes on various surfaces. Electrolytes from immersion tests will be analyzed by the inductively coupled plasma emission spectroscopy (ICP-ES) technique to determine the nature and concentration of various cations eluted during corrosion. The data will be interpreted thermodynamically to identify the electrochemical mechanism(s) of corrosion. Statistical analysis of the data will be performed to determine the effects of alloy composition and structure and their interaction effects on various corrosion parameters and to describe the difference among alloys on the basis of these parameters. These studies will contribute to a better understanding of the corrosion process of these alloys in vivo, and its possible contribution to adverse biological reactions.a